Fix list on terminals that don't disable line wrapping

src/list/state.rs

@@ -13,7 +13,7 @@ use std::{
 use crate::{
     app_state::AppState,
     exercise::Exercise,
-    term::{progress_bar, terminal_file_link},
+    term::{progress_bar, terminal_file_link, CountedWrite, MaxLenWriter},
     MAX_EXERCISE_NAME_LEN,
 };
 
@@ -28,14 +28,6 @@ fn next_ln(stdout: &mut StdoutLock) -> io::Result<()> {
     Ok(())
 }
 
-// Avoids having the last written char as the last displayed one when the
-// written width is higher than the terminal width.
-// Happens on the Gnome terminal for example.
-fn next_ln_overwrite(stdout: &mut StdoutLock) -> io::Result<()> {
-    stdout.write_all(b" ")?;
-    next_ln(stdout)
-}
-
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum Filter {
     Done,
@@ -164,40 +156,44 @@ impl<'a> ListState<'a> {
             .skip(self.row_offset)
             .take(self.max_n_rows_to_display)
         {
+            let mut writer = MaxLenWriter::new(stdout, self.term_width as usize);
+
             if self.selected_row == Some(self.row_offset + n_displayed_rows) {
-                stdout.queue(SetBackgroundColor(Color::Rgb {
+                writer.stdout.queue(SetBackgroundColor(Color::Rgb {
                     r: 40,
                     g: 40,
                     b: 40,
                 }))?;
-                stdout.write_all("🦀".as_bytes())?;
+                // The crab emoji has the width of two ascii chars.
+                writer.add_to_len(2);
+                writer.stdout.write_all("🦀".as_bytes())?;
             } else {
-                stdout.write_all(b"  ")?;
+                writer.write_ascii(b"  ")?;
             }
 
             if exercise_ind == current_exercise_ind {
-                stdout.queue(SetForegroundColor(Color::Red))?;
-                stdout.write_all(b">>>>>>>  ")?;
+                writer.stdout.queue(SetForegroundColor(Color::Red))?;
+                writer.write_ascii(b">>>>>>>  ")?;
             } else {
-                stdout.write_all(b"         ")?;
+                writer.write_ascii(b"         ")?;
             }
 
             if exercise.done {
-                stdout.queue(SetForegroundColor(Color::Green))?;
-                stdout.write_all(b"DONE     ")?;
+                writer.stdout.queue(SetForegroundColor(Color::Green))?;
+                writer.write_ascii(b"DONE     ")?;
             } else {
-                stdout.queue(SetForegroundColor(Color::Yellow))?;
-                stdout.write_all(b"PENDING  ")?;
+                writer.stdout.queue(SetForegroundColor(Color::Yellow))?;
+                writer.write_ascii(b"PENDING  ")?;
             }
 
-            stdout.queue(SetForegroundColor(Color::Reset))?;
+            writer.stdout.queue(SetForegroundColor(Color::Reset))?;
 
-            stdout.write_all(exercise.name.as_bytes())?;
-            stdout.write_all(&SPACE[..self.name_col_width + 2 - exercise.name.len()])?;
+            writer.write_str(exercise.name)?;
+            writer.write_ascii(&SPACE[..self.name_col_width + 2 - exercise.name.len()])?;
 
-            terminal_file_link(stdout, exercise.path, Color::Blue)?;
+            terminal_file_link(&mut writer, exercise.path, Color::Blue)?;
 
-            next_ln_overwrite(stdout)?;
+            next_ln(stdout)?;
             stdout.queue(ResetColor)?;
             n_displayed_rows += 1;
         }
@@ -213,10 +209,11 @@ impl<'a> ListState<'a> {
         stdout.queue(BeginSynchronizedUpdate)?.queue(MoveTo(0, 0))?;
 
         // Header
-        stdout.write_all(b"  Current  State    Name")?;
-        stdout.write_all(&SPACE[..self.name_col_width - 2])?;
-        stdout.write_all(b"Path")?;
-        next_ln_overwrite(stdout)?;
+        let mut writer = MaxLenWriter::new(stdout, self.term_width as usize);
+        writer.write_ascii(b"  Current  State    Name")?;
+        writer.write_ascii(&SPACE[..self.name_col_width - 2])?;
+        writer.write_ascii(b"Path")?;
+        next_ln(stdout)?;
 
         // Rows
         let iter = self.app_state.exercises().iter().enumerate();
@@ -237,7 +234,7 @@ impl<'a> ListState<'a> {
             next_ln(stdout)?;
 
             progress_bar(
-                stdout,
+                &mut MaxLenWriter::new(stdout, self.term_width as usize),
                 self.app_state.n_done(),
                 self.app_state.exercises().len() as u16,
                 self.term_width,
@@ -247,59 +244,55 @@ impl<'a> ListState<'a> {
             stdout.write_all(&self.separator_line)?;
             next_ln(stdout)?;
 
+            let mut writer = MaxLenWriter::new(stdout, self.term_width as usize);
             if self.message.is_empty() {
                 // Help footer message
                 if self.selected_row.is_some() {
-                    stdout.write_all(
-                        "↓/j ↑/k home/g end/G | <c>ontinue at | <r>eset exercise".as_bytes(),
-                    )?;
+                    writer.write_str("↓/j ↑/k home/g end/G | <c>ontinue at | <r>eset exercise")?;
                     if self.narrow_term {
-                        next_ln_overwrite(stdout)?;
-                        stdout.write_all(b"filter ")?;
+                        next_ln(stdout)?;
+                        writer = MaxLenWriter::new(stdout, self.term_width as usize);
+
+                        writer.write_ascii(b"filter ")?;
                     } else {
-                        stdout.write_all(b" | filter ")?;
+                        writer.write_ascii(b" | filter ")?;
                     }
                 } else {
                     // Nothing selected (and nothing shown), so only display filter and quit.
-                    stdout.write_all(b"filter ")?;
+                    writer.write_ascii(b"filter ")?;
                 }
 
                 match self.filter {
                     Filter::Done => {
-                        stdout
+                        writer
+                            .stdout
                             .queue(SetForegroundColor(Color::Magenta))?
                             .queue(SetAttribute(Attribute::Underlined))?;
-                        stdout.write_all(b"<d>one")?;
-                        stdout.queue(ResetColor)?;
-                        stdout.write_all(b"/<p>ending")?;
+                        writer.write_ascii(b"<d>one")?;
+                        writer.stdout.queue(ResetColor)?;
+                        writer.write_ascii(b"/<p>ending")?;
                     }
                     Filter::Pending => {
-                        stdout.write_all(b"<d>one/")?;
-                        stdout
+                        writer.write_ascii(b"<d>one/")?;
+                        writer
+                            .stdout
                             .queue(SetForegroundColor(Color::Magenta))?
                             .queue(SetAttribute(Attribute::Underlined))?;
-                        stdout.write_all(b"<p>ending")?;
-                        stdout.queue(ResetColor)?;
+                        writer.write_ascii(b"<p>ending")?;
+                        writer.stdout.queue(ResetColor)?;
                     }
-                    Filter::None => stdout.write_all(b"<d>one/<p>ending")?,
+                    Filter::None => writer.write_ascii(b"<d>one/<p>ending")?,
                 }
 
-                stdout.write_all(b" | <q>uit list")?;
-
-                if self.narrow_term {
-                    next_ln_overwrite(stdout)?;
+                writer.write_ascii(b" | <q>uit list")?;
             } else {
-                    next_ln(stdout)?;
-                }
-            } else {
-                stdout.queue(SetForegroundColor(Color::Magenta))?;
-                stdout.write_all(self.message.as_bytes())?;
+                writer.stdout.queue(SetForegroundColor(Color::Magenta))?;
+                writer.write_str(&self.message)?;
                 stdout.queue(ResetColor)?;
-                next_ln_overwrite(stdout)?;
-                if self.narrow_term {
                 next_ln(stdout)?;
             }
-            }
+
+            next_ln(stdout)?;
         }
 
         stdout.queue(EndSynchronizedUpdate)?.flush()

src/term.rs

@@ -15,9 +15,83 @@ thread_local! {
     static VS_CODE: Cell<bool> = Cell::new(env::var_os("TERM_PROGRAM").is_some_and(|v| v == "vscode"));
 }
 
+pub struct MaxLenWriter<'a, 'b> {
+    pub stdout: &'a mut StdoutLock<'b>,
+    len: usize,
+    max_len: usize,
+}
+
+impl<'a, 'b> MaxLenWriter<'a, 'b> {
+    #[inline]
+    pub fn new(stdout: &'a mut StdoutLock<'b>, max_len: usize) -> Self {
+        Self {
+            stdout,
+            len: 0,
+            max_len,
+        }
+    }
+
+    // Additional is for emojis that take more space.
+    #[inline]
+    pub fn add_to_len(&mut self, additional: usize) {
+        self.len += additional;
+    }
+}
+
+pub trait CountedWrite<'a> {
+    fn write_ascii(&mut self, ascii: &[u8]) -> io::Result<()>;
+    fn write_str(&mut self, unicode: &str) -> io::Result<()>;
+    fn stdout(&mut self) -> &mut StdoutLock<'a>;
+}
+
+impl<'a, 'b> CountedWrite<'b> for MaxLenWriter<'a, 'b> {
+    fn write_ascii(&mut self, ascii: &[u8]) -> io::Result<()> {
+        let n = ascii.len().min(self.max_len.saturating_sub(self.len));
+        self.stdout.write_all(&ascii[..n])?;
+        self.len += n;
+        Ok(())
+    }
+
+    fn write_str(&mut self, unicode: &str) -> io::Result<()> {
+        if let Some((ind, c)) = unicode
+            .char_indices()
+            .take(self.max_len.saturating_sub(self.len))
+            .last()
+        {
+            self.stdout
+                .write_all(&unicode.as_bytes()[..ind + c.len_utf8()])?;
+            self.len += ind + 1;
+        }
+
+        Ok(())
+    }
+
+    #[inline]
+    fn stdout(&mut self) -> &mut StdoutLock<'b> {
+        self.stdout
+    }
+}
+
+impl<'a> CountedWrite<'a> for StdoutLock<'a> {
+    #[inline]
+    fn write_ascii(&mut self, ascii: &[u8]) -> io::Result<()> {
+        self.write_all(ascii)
+    }
+
+    #[inline]
+    fn write_str(&mut self, unicode: &str) -> io::Result<()> {
+        self.write_all(unicode.as_bytes())
+    }
+
+    #[inline]
+    fn stdout(&mut self) -> &mut StdoutLock<'a> {
+        self
+    }
+}
+
 /// Terminal progress bar to be used when not using Ratataui.
-pub fn progress_bar(
-    stdout: &mut StdoutLock,
+pub fn progress_bar<'a>(
+    writer: &mut impl CountedWrite<'a>,
     progress: u16,
     total: u16,
     line_width: u16,
@@ -32,9 +106,13 @@ pub fn progress_bar(
     const MIN_LINE_WIDTH: u16 = WRAPPER_WIDTH + 4;
 
     if line_width < MIN_LINE_WIDTH {
-        return write!(stdout, "Progress: {progress}/{total} exercises");
+        writer.write_ascii(b"Progress: ")?;
+        // Integers are in ASCII.
+        writer.write_ascii(format!("{progress}/{total}").as_bytes())?;
+        return writer.write_ascii(b" exercises");
     }
 
+    let stdout = writer.stdout();
     stdout.write_all(PREFIX)?;
 
     let width = line_width - WRAPPER_WIDTH;
@@ -77,16 +155,20 @@ pub fn press_enter_prompt(stdout: &mut StdoutLock) -> io::Result<()> {
     Ok(())
 }
 
-pub fn terminal_file_link(stdout: &mut StdoutLock, path: &str, color: Color) -> io::Result<()> {
+pub fn terminal_file_link<'a>(
+    writer: &mut impl CountedWrite<'a>,
+    path: &str,
+    color: Color,
+) -> io::Result<()> {
     // VS Code shows its own links. This also avoids some issues, especially on Windows.
     if VS_CODE.get() {
-        return stdout.write_all(path.as_bytes());
+        return writer.write_str(path);
     }
 
     let canonical_path = fs::canonicalize(path).ok();
 
     let Some(canonical_path) = canonical_path.as_deref().and_then(|p| p.to_str()) else {
-        return stdout.write_all(path.as_bytes());
+        return writer.write_str(path);
     };
 
     // Windows itself can't handle its verbatim paths.
@@ -97,14 +179,18 @@ pub fn terminal_file_link(stdout: &mut StdoutLock, path: &str, color: Color) ->
         canonical_path
     };
 
-    stdout
+    writer
+        .stdout()
         .queue(SetForegroundColor(color))?
         .queue(SetAttribute(Attribute::Underlined))?;
-    write!(
-        stdout,
-        "\x1b]8;;file://{canonical_path}\x1b\\{path}\x1b]8;;\x1b\\",
-    )?;
-    stdout
+    writer.stdout().write_all(b"\x1b]8;;file://")?;
+    writer.stdout().write_all(canonical_path.as_bytes())?;
+    writer.stdout().write_all(b"\x1b\\")?;
+    // Only this part is visible.
+    writer.write_str(path)?;
+    writer.stdout().write_all(b"\x1b]8;;\x1b\\")?;
+    writer
+        .stdout()
         .queue(SetForegroundColor(Color::Reset))?
         .queue(SetAttribute(Attribute::NoUnderline))?;